Sequencing batch reactor with continuous membrane filtration and solids reduction

ABSTRACT

A method and system of treating wastewater that can provide operating flexibility is disclosed. The system is operated with a sequencing batch reactor, which is typically cycling to any of fill, react, settle, decant, and idle stages, to treat the wastewater. The system can further utilize a membrane filtration system to further treat water from the sequencing batch reactor and produce suitable water. A solids-reducing system can be connected to the sequencing batch reactor and reduce an amount of biodegraded solids by converting the character or distribution of microorganisms population in the biomass.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/823,268, filed Aug. 23, 2006, entitled COMBINATION OF A FIVE STAGESEQUENCING BATCH REACTOR WITH CONTINUOUS MEMBRANE FILTRATION, the entirecontents of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and processes of wastewatertreatment and, in particular, to systems and methods of treatingwastewater utilizing sequencing batch reactors with membrane filtrationsystems.

2. Description of the Related Art

Pilgram et al., in U.S. Pat. No. 6,383,389, which is incorporated hereinby reference, teach a wastewater treatment system and method ofcontrolling the treatment system. A control system can sequence andsupervise treatment steps in a batch flow mode of operation or acontinuous flow mode of operation.

Daigger et al., in U.S. Pat. No. 6,517,723, teach a method and apparatusfor treating wastewater using membrane filters. The apparatus includes abioreactor for containing a mixture of wastewater under treatment andactivated sludge. The bioreactor is divided into a plurality of seriallyconnected treatment zones. A membrane filter is downstream of an aerobiczone of the bioreactor.

Mikkelson et al., in U.S. Pat. Nos. 6,613,222 and 6,875,357, teach aprocess and apparatus for the treatment of wastewater. A three-phasecycle, including a mix fill phase, a react fill phase, and reactdischarge phase, is used. The need for separate basins for anaerobic andanoxic conditions, and a quiescent environment for solids/liquidseparation as in conventional sequencing batch reactor systems iseliminated.

Johnson et al., in U.S. Pat. No. 7,014,763, teach multiple barrierbiological treatment systems. In a sequencing batch reactor system, theactivated sludge, biochemical reaction stages are separated from andindependent of the clarification and sedimentation stages.

Dimitriou et al., in U.S. Pat. Nos. 7,118,674 and 7,179,370, disclose anenergy-efficient biological treatment with membrane filtration apparatusand process. The biological treatment section is physically separatedfrom the filtration section.

DiMassimo et al., in U.S. Pat. No. 7,147,778, disclose a method andsystem for nitrifying and denitrifying wastewater. The system hasreactors that nitrify or denitrify wastewater and a membrane reactorthat operates under aerobic conditions.

Reid, in U.S. Pat. No. 7,156,998, teaches a phased activated sludgesystem that incorporates batch treatment techniques in a flow-throughprocess. The mixing and aeration systems are independent to facilitatethe operation of the main reactor vessel in aerated and anoxicconditions.

SUMMARY OF THE INVENTION

One or more aspects of the invention involve embodiments of a wastewatertreatment system comprising a source of wastewater, at least onesequencing batch reactor fluidly connected to the source of wastewater,a membrane filter system fluidly connectable to the sequencing batchreactor, and a solids reduction system comprising at least onebiological reactor fluidly connectable to the sequencing batch reactor.

Other aspects of the invention can involve a method of treatingwastewater comprising introducing wastewater to be treated into abiological reactor, aerating at least a portion of the wastewater topromote conversion of at least a portion of undesirable components inthe wastewater into a first biomass in the biological reactor, allowingat least a portion of the first biomass to settle in the biologicalreactor thereby producing a solids-rich liquor and a solids-lean liquor,transferring at least a portion of the solids-lean liquor into amembrane filtration system, and transferring at least a portion of thesolids-rich liquor into a biological solids reduction system.

Further aspects of the invention can involve a method of facilitatingwastewater treatment comprising providing a membrane filtration systemcomprising a retentate liquor outlet, fluidly connecting the membranefiltration system downstream of a sequencing batch reactor system,fluidly connecting a retentate liquor outlet of the membrane filtrationsystem to an inlet of the sequencing batch reactor system, andconnecting a solids-reducing biological system to a sludge outlet of thesequencing batch reactor system.

Still further aspects of the invention can involve a wastewatertreatment system comprising a first biological conversion systemcomprising a sequencing batch reactor fluidly connected to a membranefiltration unit, and a second biological conversion system fluidlyconnected to the first biological conversion system. The secondbiological conversion system can comprise a facultative biologicalreactor.

Other further aspects of the invention can involve a method of treatingwater comprising filling a basin of a sequencing batch reactor withwater to be treated to form mixed liquor, aerating the mixed liquor inthe basin to promote biological activity therein, allowing at least aportion of the solids in the mixed liquor to settle into a solids-richsludge layer below a solids-lean water layer, decanting at least aportion of the solids-lean water, and contacting the decantedsolids-lean water to a membrane filtration system.

In accordance with still further aspects, the invention can involve amethod of treating water comprising filling a basin of a sequencingbatch reactor with water to be treated to form mixed liquor, aeratingthe mixed liquor in the basin to promote biological activity therein,decanting from the basin a solids-lean water stream formed afterallowing at least a portion of the solids to settle into a solids-richsludge layer, transferring at least a portion of the solids-rich sludgeinto a bioreactor, and converting a microorganism populationdistribution of the solids-rich sludge into a facultative-organismdominant population distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Theidentical or nearly identical component or feature that is illustratedin various figures is represented by a like numeral. For purposes ofclarity, not every component may be labeled in every drawing, nor isevery component of each embodiment of the invention shown whereillustration is not necessary to allow those of ordinary skill in theart to understand the invention. In the drawings:

FIG. 1 is a block flow diagram illustrating a representative treatmentsystem pertinent to one or more aspects of the invention;

FIG. 2 is a block flow diagram illustrating a representative sequence ofstages of a sequencing batch reactor pertinent to one or more aspects ofthe invention;

FIG. 3 is a block flow diagram illustrating a representative membranefiltration system pertinent to one or more aspects of the invention; and

FIG. 4 is a block flow diagram illustrating a representativesolids-reducing system pertinent to one or more aspects of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

This invention is directed to systems and methods of treating water to,for example, reduce oxygen demand, such as the biological oxygen demand(BOD), and render the water suitable for secondary uses or discharge tothe environment. One or more aspects of the invention relate towastewater treatment systems and methods of operation and facilitatingthereof. The invention is not limited in its application to the detailsof construction and the arrangement of components, systems, orsubsystems set forth herein, and is capable of being practiced or ofbeing carried out in various ways. Typically, the water to be treated,such as wastewater or a wastewater stream, contains waste matter which,in some cases, can comprise solids and soluble and insoluble organic andinorganic material. Prior to discharge to the environment, such streamsmay require treatment to decontaminate or at least partially render thewastewater streams benign or at least satisfactory for discharge underestablished regulatory requirements or guidelines. For example, thewater can be treated to reduce its BOD or other characteristic such asGiardia content to within acceptable limits.

Some aspects of the invention can involve biologically treatingwastewater by promoting bacterial digestion of biodegradable material ofat least a portion of at least one species in the wastewater. Furtheraspects of the invention can relate to effecting or at leastfacilitating separation of converted, digested biodegraded solidmaterial from the entraining liquid. Still further aspects of theinvention can relate to effecting or at least facilitating reducing anamount of solids from the wastewater.

As used herein, the terms “water” and “wastewater” refer to water to betreated such as streams or bodies of water from residential, commercial,or municipal, industrial, and agricultural sources, as well as mixturesthereof, that typically contain at least one undesirable species, orpollutant, comprised of biodegradable, inorganic or organic, materialswhich can be decomposed or converted by biological processes intoenvironmentally benign or at least less objectionable compounds. Thewater to be treated can also contain biological solids, inert materials,organic compounds including recalcitrant or a class of compounds thatare difficult to biodegrade relative to other organic compounds as wellas constituents from ancillary treatment operations such as, but notlimited to, nitrosamines.

A “solids-lean” liquor is typically water having less suspended solidsrelative to a starting mixed liquor after one or more settling orseparation operations. Conversely, a “solids-rich” liquor, which is alsoreferred to herein as “sludge,” is typically water having a highersolids concentration relative to a starting mixed liquor after one ormore settling or separation operations. For example, a mixed liquorhaving suspended solids can be allowed to promote settling of at least aportion of the solids suspended therein; the resultant water body, as aconsequence of artificially induced or natural gravitational forces willtypically have a lower water layer and an upper water layer, wherein thelower sludge layer has a higher concentration of solids, relative to thestarting mixed liquor and to the upper, solids-lean water layer.Further, the solids-lean water layer will typically have a lowerconcentration of solids suspended therein relative to the starting mixedliquor.

The inventive systems can comprise one or more biologically-based unitoperations. The systems and techniques of the invention can be effectedas, or at least as a portion, of decontamination or treatment systemsthat typically include one or more of pre-treatment, primary treatment,secondary treatment, and post-treatment or polishing operations.Further, the treatment facilities that can employ one or more aspects ofthe invention can include at least one of the pre-treatment, primarytreatment, secondary treatment, and post-treatment or polishingoperations.

Pretreatment systems and operations may remove grit, sand, and gravel.Primary treatment operations or systems can involve at least partialequalization, neutralization, and/or removal of large insoluble materialof the water to be treated such as, but not limited to fats, oils, andgrease. The pretreatment and primary treatment operations may becombined to remove such materials as well as settlable solids andfloating bodies, and insoluble objects such as rags and sticks. Primaryclarifiers may be utilized to separate larger solids.

Secondary treatment unit operations or systems can involve biologicaldigestion or biological treatment such as those that typically employ abiomass with bacteria to at least partially digest or convertbiodegradable material such as, but not limited to, sugar, fat, organicmolecules, and compounds that create an oxygen demand. Indeed someadvantageous aspects of the invention can utilize biological processesand systems to remove, convert or neutralize at least a portion oforganic material in the water to be treated.

Some embodiments of the treatment systems of the invention can comprisea first biological conversion train or system comprising a sequencingbiological reactor fluidly and a second biological conversion train orsystem fluidly connected to the first biological conversion system. Thefirst biological conversion system can further comprise or be connectedto one or more membrane filtration units. The second biologicalconversion system can comprise one or more unit operations that reducean amount of solids with one or more facultative biological reactors.

One or more embodiments pertinent to some aspects of the invention caninvolve a method of treating wastewater comprising one or more acts orsteps of introducing wastewater to be treated into a biological reactor,aerating at least a portion of the wastewater to promote conversion ofat least a portion of undesirable components in the wastewater into afirst biomass in the biological reactor, allowing at least a portion ofthe first biomass to settle in the biological reactor thereby producinga solids-rich liquor and a solids-lean liquor. At least a portion of thesolids-lean liquor can be transferred into a membrane filtration system.Optionally, at least a portion of the solids-rich liquor or sludge canbe transferred into a biological solids-reducing system.

One or more embodiments pertinent to other aspects of the invention caninvolve a wastewater treatment system comprising a source of wastewaterand at least one bioreactor, such as sequencing batch reactors, fluidlyconnected to the source of wastewater. The treatment system can furthercomprise at least one membrane filtration system fluidly connectable toat least one of the sequencing batch reactors. In some cases, thetreatment system can further comprise a solids reduction system with atleast one biological reactor fluidly connectable to the sequencing batchreactor. The treatment system may further comprise a controlleroperatively coupled to control the sequencing batch reactor in, forexample, a settle or decant stage.

In still further embodiments of the invention, the method and techniquesof the invention can comprise providing a membrane filtration systemcomprising a retentate liquor outlet and, in some cases, fluidlyconnecting the membrane filtration system downstream of a sequencingbatch reactor system. The retentate liquor outlet of the membranefiltration system can be fluidly connected to an inlet of the sequencingbatch reactor system. A solids-reducing biological system can optionallybe connected to a sludge outlet of the sequencing batch reactor system.A solids-reducing system can also be connected to one or more of thebiological reactors to at least partially reduce an overall amount ofsolids recovered or removed from the water to be treated therebyreducing a burden on an amount of solids to be disposed or discharged toa landfill.

Still further aspects of the invention can be considered as biologicallytreating nitrogen-based compounds, separating a liquid product, and/orseparating a solids-rich product from the water to be treated. Otheraspects of the invention can be considered as decoupling operationalinteraction or dependencies between the biologically-based treatmentsystems and processes from the solids and liquids separation systems andprocesses. Further aspects of the invention can be considered asproviding operational flexibility between, for example, biological unitoperations from filtration unit operations of a treatment facility.Still further aspects of the invention can be considered as furtherreducing an overall amount of solids discharged as a consequence oftreating water.

Alternative aspects of the invention may be regarded as biologicallytreating water to promote degradation or conversion of biodegradablematerial, followed by settling and/or decanting the mixed liquorcomprising the converted material; and in further aspects, as filtrationof a solids-lean liquor to produce permeate that can be regarded astreated water. Such aspects of the invention can be contrasted toconventional membrane bioreactor systems (MBR), which seek to avoid thesettling and decanting stages by substituting therefor a membranefiltration system downstream of a first anaerobic stage that istypically followed by an anoxic stage and, in some cases, an aerobicstage. In further contrast to MBR systems, which involves and promotesbiological reactions within and during the filtration operation, someaspects of the invention pertain to filtering a low solids-contentwater, having essentially no biological activity occurring therein.

Mixed liquor having suspended solids can be recycled from the membranefiltration stage to the aerobic stage, a portion of the liquor from thesecond aerobic stage is typically introduced into the anoxic stage, anda portion of the liquor in the anoxic stage is introduced with the waterto be treated into anaerobic stage.

The systems and components of the invention may also provide costadvantages relative to MBR systems by facilitating the use of lower costmembranes. For example, a larger pore size or more open weave membranemay be utilized rather than costlier, smaller pore size membranes. Themembranes can, for example, comprise polyethylene, polypropylene,polysulfone, polyamide, polyvinylidene fluoride, and in some cases,copolymers, mixtures, and blends thereof.

Lower operating costs, relative to MBR systems, may also be realizedbecause less energy would be required to aerate and/or transfer, as in arecycle stream, because the liquid to be filtered has a relatively lowersolids concentration which typically has a lower viscosity. Indeed,advantageous aspects of the invention can be directed to filteringliquor that has less than 5 wt % solids suspended therein. The lowsolids liquor to be filtered can thus be characterized as having a lowerviscosity relative to suspended solids mixed liquor, commonly referredto as MLSS. For example, some aspects of the invention inventivelyfilter clarified water or liquor, having a viscosity that is within 10%of the viscosity of clean water, rather than MLSS that is characterizedby having a higher viscosity. The lower viscosity approach associatedwith the systems and techniques of present treatment system, in turn,provides reduced costs as a result of a lower aeration burden and lowerpumping loads, compared to conventional MBR systems. Increasedreliability can also be realized because filtering a lowersolids-content water stream, relative to conventional MBR liquor,potentially reduces the amount of undesirable biofilm and solidsaccumulation. Indeed, lower solids accumulation or membrane coatingrates further reduces operational cleaning requirements, leading tofurther cost benefits.

Particularly advantageous embodiments of the invention can involve awater or wastewater treatment system comprising a biological treatmenttrain fluidly connected to a source of water or wastewater to be treatedcontaining undesirable biodegradable material. The biological treatmenttrain typically comprises a bioreactor having a biomass thatmetabolically converts biodegradable material by, for example,nitrification and de-nitrification metabolic pathways, to lessobjectionable solids and water. The treatment system can comprise asolids-removal train that separates solids from liquids of a solids-leanstream or body of water treated in the biological conversion train.Further, the treatment system can comprise a solids-reducing train thatreduces an amount of collected solids generated or treated duringbacterial conversion of the biodegradable material in the biologicaltreatment train. Operationally favorable treatment systems can alsocomprise one or more solids-collecting trains that separate solids fromany of the solids-reducing train, the solids-removal train, and thebiological treatment train.

FIG. 1 exemplarily illustrates an embodiment in accordance with someaspects of the invention. The treatment system 10 can be fluidlyconnected to a source 102 of water to be treated. In accordance with anyone of the aforementioned aspects of the invention, treatment system 10can comprise one or more biological treatment or conversion trains 110and, optionally, one or more solids-removal systems or trains 120,typically fluidly connected to one or more unit operations of biologicaltreatment train 110. Treatment system 10 can further comprise one ormore solids-reducing systems or trains 130, which are connected or atleast connectable to one or more unit operations of any of thebiological train 110 and solids-removal train 120. In some embodiments,treatment system 10 can further comprise one or more solids-collectingsystems or trains 140, fluidly connected or connectable downstream ofone or more unit operations of any of biological treatment train 110,solids-removal train 120, and solids-reducing train 130. Treated watercan be retrieved from solids-removal train 120 and delivered to storageor a point of use 104 such as a secondary use involving irrigation, ordischarged to the environment.

Source 102 of water to be treated can be any of a water collectionsystem from any one or more of a municipality, a residential community,and an industrial or a commercial facility, and an upstreampre-treatment system, or combinations thereof. For example, source 102can be sedimentation or settling tank receiving water from a sewersystem.

Biological treatment train 110 can be any combination of continuous andbatch biological processes. Thus, in accordance with some aspects,biological treatment train 110 can comprise at least one bioreactor thatcontains or is configured to contain a biomass of microorganisms thatmetabolize biodegradable materials in the water to be treated.Biological treatment train 110 can comprise a series of zones each ofwhich can be configured to provide any one or more of aerobic,anaerobic, and anoxic conditions to preferentially promote correspondingbacterial metabolic activity. For example, biological treatment train110 can serially comprise a first zone typically disposed to receivewater to be treated and configured to promote anaerobic bacterialactivity therein; a second zone that promotes anoxic bacterial activity;a third zone that preferentially favors aerobic bacterial activity; anda gravity separator or settling zone from which treated effluent isdecanted and settled sludge is returned to an upstream zone. Further,the biological treatment train can comprise fixed film systems such astrickling filters and biological contactors.

Other advantageous embodiments may involve biological treatment trainsthat utilize batch treatment processes having at least two stagesperformed in a single reactor or basin. Thus, in accordance with someaspects of the invention, treatment train 110 can comprise one or moresequencing batch reactors (SBR) 112 optionally operatively coupled toand regulated by at least one controller or control system 114.

As exemplarily illustrated in FIG. 2, SBR 112 can be operated orconfigured to receive the water to be treated from source 102 in a firststage (illustrated as stage “1”), which is typically referred to as aFILL stage. Fill stage “1” can be performed in aerated, anoxic or acombination of aerated and anoxic conditions. Preferably, the influentwater to be treated is introduced into the basin 216 of batch reactor112 through one or more influent distribution manifolds 217. Basin 216can be sized to accommodate or provide a desired hydraulic retentiontime and to accommodate the volume and incoming flow rate of water to betreated.

When basin 216 is at least partially filled or thereafter, SBR 112 canbe operated to favor bacterial metabolism that converts or digestbiodegradable material in a second stage (illustrated as stage “2”),which is typically referred to as a REACT stage. React stage “2” can beperformed under aerobic conditions by introducing oxygen, preferably asair from one or more air sources 151 through aeration manifold 253submerged in the liquor. React stage “2” can be performed for a periodsufficient to promote at least partial biodegradation of the material.For example, aeration can be performed to create aerobic conditions tofacilitate oxidation of ammonia to nitrite by ammonia-oxidizingbacteria. Air source 151 preferably further provides air releasedthrough aeration manifold 253 as air bubbles 255 in amounts sufficientto induce mixing of the liquor within basin 216. Alternatively, or inconjunction with the aeration induced phenomena, mixing can also beeffected by a mixer, such as an impeller (not shown), which may beadvantageous when mixing is desired without introducing air into theliquor.

A SETTLE stage (illustrated as stage “3”) typically follows the aerationand/or mixing stage to create quiescent conditions that allow biomass inthe liquor to settle to form a supernatant, solids-lean liquor layer 257above a solids-rich or sludge layer 259. The duration of settle stage“3” may vary and depend on several factors including, but not limitedto, the temperature of the mixed liquor and the nature and compositionof the biomass.

The solids-lean liquor can then be withdrawn or decanted in a DECANTstage (illustrated as stage “4”) and be further treated in, for example,solids removal train 120. At least a portion of the settled sludge 259can be withdrawn through manifold 217 and directed to further treatmentby disinfection or be discharged into the environment, such as a river.A solids-rich stream can be withdrawn and introduced intosolids-reducing train 130. Withdrawal or decanting of the treatedeffluent or solids-lean liquor 257 can preferably be performed utilizinga floating solids-excluding decanter or skimmer (not shown) that ispreferably constructed to have apertures that do not or at least reducesthe likelihood of turbulent conditions that disturb the settledsolids-rich layer.

An IDLE stage (illustrated as stage “5”) may be optionally includedduring instances the SBR 112 waits to receive influent to be treated.

In some cases, any of the functions or activities can be performed inmore than one stage. For example, withdrawing a solids-rich sludge canbe performed during settling stage “3” as well as during idle stage “5”.Thus, the invention can be practiced in other than the sequence ofstages presented herein. Further, any or more stages can be omitted orcombined. For example, in some cases, react stage “2” can be performedduring fill stage “1” thereby combining or extending the duration of thereact stage.

Preferably, some aspects of the invention can advantageously promotebacterial activity to effect nitrification and de-nitrification. Thebiomass in any one of the stages typically comprises a mixture ofbacteria. Further, each of the stages may have a different biomassconstituency. Thus, for example, the biomass during or after react stage“2” may comprise obligate aerobes, facultative aerobes, and aerotolerantmicroorganisms. The nitrification and de-nitrification process can befacilitated by microorganisms of the genera Nitrosomonas andNitrobacter.

The OMNIFLOW® sequencing batch reactor system from Siemens WaterTechnologies Corp., Edwardsville, Kans., is an example of a commerciallyavailable treatment system that can comprise the biological train usedto effect biological nutrient removal in accordance with some aspects ofthe invention. Further aspects of the invention may utilize the systemsand methods disclosed by any of Calltharp and Calltharp et al. in U.S.Pat. Nos. 4,775,467, 5,021,161, and 6,884,354, each of which isincorporated herein by reference. Indeed, some advantageous featurespertaining to constant level SBR systems may be utilized. Such constantlevel biological conversion systems may advantageously provide evenfurther improved process control of the overall treatment system byreducing any operational fluctuations or variations during downstreamfiltration operations. Further advantages can, in some cases, reduce thesize any equalization tanks, or even eliminate the need for such unitoperations, which reduces the overall treatment system footprint andcapital requirements.

Sequencing the various stages may be facilitated by utilizing one ormore controllers 114 operatively coupled to the one or more sequencingbatch reactors 112. One or more sensors are typically utilized in orwith the one or more unit operations of SBR 112 to provide an indicationor characteristic of the state or condition of processes duringbiological treatment processes. For example, one or more levelindicators (not shown) can be disposed in basin 216 and configured totransmit to the one or more controllers 114 a representation of theliquid level contained within basin 216. Controller 114 can, based onthe signals received from the one or more sensors, generate and sendcontrol signals to any of the components or even ancillary systems oftrain 110. For example, at a high liquid level condition in basin 216,as measured by the one or more level indicators, controller 114 cangenerate and transmit a control signal to an actuator that closes aninlet valve fluidly isolating source 102 and basin 216. Controller 114typically further generates the control signals that initiates andterminates the stages of one or more SBRs 112. For example, controller114 can generate and transmit a control signal to energize orde-energize air source 251.

Solids-lean liquor decanted from basin 216 can be further treated insolids-removal train 120 and, in some cases, selectively retainsundesirable microorganism such as those of the genera Cryptosporidiumand Giardia or otherwise reduce the concentration of pathogenic speciesin the treated permeate. As shown in FIG. 3, train 120 preferablycomprises at least one membrane filtration system 122 having one or moremembrane cassettes or modules 322, typically at least partially immersedin the liquid to be filtered contained in a vessel 324 of filtrationsystem 122. Module 322 typically comprises a plurality of membranes 325having a microporous structure which selectively inhibits any solids andallows water to permeate therethrough. Permeate or treated water havingdesirable characteristics can be withdrawn from membrane module 322 andat least a portion thereof delivered to storage or secondary use 104 ordischarged to the environment. For example, treated water can be used toirrigate vegetation. In some cases, however, the treated water can befurther purified or treated in one or more downstream unit operationssuch as, but not limited to, evaporative systems, electrodeionizationsystems, disinfection systems such as those that irradiate withultraviolet radiation or raise the temperature of the stream toinactivate any contaminants, and pressure-driven processes like thoseutilizing reverse osmosis, nanofiltration, and ultrafiltration.

A pressure differential from the unfiltered liquor side to the permeateside of the membrane effects the filtration. This transmembrane pressuredifferential can be effected by applying a higher pressure against theliquor, relative the permeate pressure, and/or by applying vacuumpressure at the permeate side of the membrane while providingatmospheric pressure over the liquor or retentate side.

Typically each module has horizontally or vertically oriented membranefibers, each having millions of microscopic pores. Water or liquorhaving low-solids concentration to be removed is filtered by applying aslight vacuum to one or more ends of each of the membrane fibers,thereby drawing the water as permeated through the microscopic pores andacross the membrane walls and into an internal fiber cavity. Themicropores typically inhibit unwanted solids such as bacteria, viruses,fecal coliforms, and other pathogens, from passing through but allowingwater to pass.

Feed water flows into the membrane tank and treated water is drawnthrough the membranes by applying a vacuum to the inside of the membranefibers. In some cases, the permeate water retrieved by filtration can bereplaced with water to be filtered, typically from an equalization tank,to maintain a constant liquor level.

Train 120 can optionally comprise one or more surge vessels to de-couplethe biological treatment operations from the filtration operations. Forexample, one or more equalization tanks 124 can be fluidly connecteddownstream of basin 216 and upstream of membrane filtration system 122.Tank 124 can thus receive solids-lean liquor during the settle or idlestages. Liquor can thus be introduced into the filtration system 122continuously or continually, rather than intermittently. Such aconfiguration can advantageously reduce the flux requirement offiltration system 122, relative to a capacity requirement that wouldhave been dictated by intermittent processing.

Normal filtration operations typically occur from an outer surface to ahollow inner core or lumen of the membrane fibers. Filtered watertypically passes through the walls of the fibers while particulates areretained on the outside of the fiber wall; particulates larger thanabout 0.1 microns are typically retained or filtered.

In some embodiments of the invention, membrane cassettes or modules 322can be cleaned in place to dislodge any solids accumulated at thesurface of membrane as a result of the filtration process. Cleaning canbe performed by introducing a scouring fluid of air, liquid, or amixture of air and liquid against the plurality of membranes 325 for aduration and at conditions sufficient remove the accumulated solids. Forexample, air from air source 351 or from source 251 can be directedthrough a potting head 327 of module 322 to membranes 325. Air or amixture of air and water can be utilized through one or more nozzles 361to aerate and/or mix liquor in vessel 324 to, for example, prevent or atleast reduce the likelihood of concentration polarization during thefiltration process. Backwashing may also be utilized to facilitate oreffect cleaning, typically automatically after a predetermined time orfiltration duration, such as after from about 15 minutes up to sixtyminutes of filtration. The backwash cycle interval and duration periodmay be dependent on liquor conditions and a particular facility mayrequire longer backwashing period or more frequent backwashingoperations because of a higher suspended solids concentration. Duringbackwashing, liquor and air can be used to scour the outer membranesurface. Optionally, vessel 324 is at least partially drained afterbackwashing and before normal filtration operations recommence.

Cleaning can also involve periodic chemical cleaning that at leastpartially dissolves or detaches any accumulated particles on themembrane surface. Chemical cleaning may be advantageously utilized wherebackwashing cannot sufficiently dislodge particles. For example, themembrane surface can be exposed to a solution with one or more oxidizerssuch as chlorine. Acids can also remove or facilitate removal ofstubborn inorganic compounds. After the chemical cleaning process, abackwash is typically utilized to remove chemical cleaning solutionsbefore recommencing normal filtration operations.

A membrane integrity test can be periodically performed to ensurereliable removal of the harmful or undesirable microorganisms orpathogens. For example, an air hold test can be performed whereincompressed air is held at about 96 kPa to detect any leaks.

A portion of the retentate liquor contained in vessel 324 can bewithdrawn continuously, continually, or intermittently, by, for example,one or more pumps 340 and transferred to train 110 through recycle line173. Typically, retentate is introduced with water to be treated fromsource 102 into the one or more bioreactors 112.

Other unit operations may utilized, in place of or along with filtrationsystem 122 to effect solid and liquid phase separation. For example, oneor more clarifiers, nanofiltration, and ultrafiltration may be utilized.

One or more controllers can be utilized to direct or regulate thefiltration processes. For example, a dedicated controller or controller114 can be configured to generate a control signal to energize orde-energize air source 351 thereby managing at least one of the rate,duration, and frequency of scouring of any of the membrane modules. Thecontroller can also be configured to manage or regulate a rate of flowof the retentate recycle into train 110 by energizing or de-energizing amotor (not shown) of pump 340 or by actuating a flow control valve (notshown) in recycle line 173.

Commercially available filtration systems that may be utilized in someembodiments of the invention to serve as barriers to removeCryptosporidium, Giardia, bacteria, turbidity, and suspended solids,include those employing the CMF-S™ continuous membrane filtrationmodules as well as the MEMCOR® CMF (Pressurized) XP, CP, and XS membranefiltration systems, from Siemens Water Technologies Corp., Windsor,Australia.

Sludge or solids-rich layer from basin 216 can be further treated in oneor more solids reduction or solids-reducing trains 130. Train 130 cancomprise one or more unit operations that reduce the amount of solids ofthe sludge. As illustrated in FIG. 4, train 130 can comprise one or morebioreactors, referred to herein as interchange bioreactor 424, each ofwhich is typically operated to create conditions that favor the growthof facultative microorganisms over the growth of obligatemicroorganisms.

Interchange bioreactor 424 or facultative biological reactor cancomprise biomass with a bacterial population distribution that isdominated by facultative aerobes, which can digest at least a portion ofthe biodegradable solids of the sludge. An interchange of biologicalsolids decomposition and re-growth is thus created that reduces theoverall amount of biological solids. The resultant sludge frominterchange bioreactor 424 typically has less solids content, relativeto the solids content of the sludge from train 110 because thefacultative microorganisms metabolize or digest the remains ofinactivated obligate aerobes and their byproducts and, in some cases,other biodegradable material.

Interchange bioreactor 424 is typically operated with conditions thatinactivate at least a portion of the obligate aerobes by, for example,controlling or reducing the dissolved oxygen content of the biomasscontained therein which, in some cases, can involve providing varyingperiods of alternating aerobic and anoxic conditions by, for example,controllably regulating air introduced thereto from, for example, an airsource (not shown). For example, the operating steps of interchangebioreactor 424 can include sludge filling, accompanied or unaccompaniedby mixing, aerating, decanting, and settling phases. Any one of thephases may last from, for example, one to four hours. Moreover, aeratingmay be performed to achieve a desired oxygen content or oxidationreduction potential. The overall process typically provides alternatingenvironments of oxygen-rich and oxygen-deficient conditions. Interchangebioreactor 424 or any component or subsystem of solids-reducing train130 can be operated in accordance with any one or more of the techniquesdisclosed by Miklos in U.S. Pat. Nos. 6,660,163, 6,833,074, and7,105,091, each of which is incorporated herein by reference.

Any portion of the resultant sludge can be reintroduced into any of theunit operations of biological treatment train 110 (such as into SBR 112)for further degradation, or to solids-collection train 140.

Alternatively advantageous embodiments may involve configurations thatutilize one or more inert solids separators 426 that remove any trash,grit, and other non-biodegradable solid materials. For example, inertsolids from a sludge stream from SBR 112 can be directed to separator426 and biomass can then be directed to interchange bioreactor 424.Non-limiting examples of unit operation that can be used to separate theinert solids include hydrocyclones, screens, and strainers. Inert solidsretrieved from separator 426 can be directed to solids-collection train140 or directly discharged into a landfill. Thus, any portion of asludge or solids-rich liquor having a biomass that is predominantlyobligate aerobes withdrawn from SBR 112, typically after the settlestage, can be introduced into interchange bioreactor 424, with orwithout further solids-liquids separation in inert solids separator 426.

The CANNIBAL™ solids reduction process, from Siemens Water TechnologiesCorp., Waukesha, Wis., is an example of a commercially available systemand process that may be utilized in accordance with some aspects of thepresent invention.

A controller may be utilized to regulate the operating parameters of anyunit operation of train 130. For example, a controller, which can becontroller 114, can be configured to generate and transmit a processcontrol signal that activates or inactivates an air source and furtherregulates a rate, duration and frequency of air delivered to interchangebioreactor 424. Indeed, advantageous embodiments in accordance with someaspects of the invention can involve measuring one or more processconditions of interchange bioreactor 424 and generating one or morecontrol signals based at least partially on the one or more measuredprocess conditions. For example, one or more both of the dissolvedoxygen and the oxidation reduction potential of the liquor ininterchange reactor 424 can be measured and transmitted to controller114, which can then generate and transmit a control signal to one ormore air sources or systems to achieve a target or desired value in theliquor of the interchange reactor 424. The aforementioned control loopcan be nested within or applied in conjunction with a control schedulethat is configured to provide the desired microorganism populationdistribution.

Solids-collecting train 140 can comprise one or more polishing ordewatering unit operations, thickeners, or solids-liquid separators 128such as hydrocyclones, clarifiers, drying beds, and lagoons which canfurther increase the solids concentration or remove water from solids tobe discharged or disposed to, for example, a landfill 150. In someembodiments, one or more membrane filter modules may be used to separatethe solid phase from the liquid phase of the sludge from system 10.

Other unit operations such as filters and strainers may also be utilizedin train 140. The precipitated or collected solids can be disposed assludge. Further, a controller can facilitate or regulate the operatingparameters of train 140. Thus, for example, controller 114 may beconfigured to adjust a rate of addition of the one or more treatingagents.

Controller 114 may respond to signals from timers (not shown) and orsensors (not shown) positioned at any particular location withintreatment system 10. For example, a sensor positioned in interchangebioreactor 424 may indicate less than optimum conditions therein. Theone or more sensors may monitor one or more operational parameters suchas pressure, temperature, one or more characteristics of the liquor,and/or one or more characteristics of the effluent. Similarly, a sensor(not shown) disposed in or otherwise positioned with recycle 173 toindicate a flow rate thereof at, below, or above a desired or targetrate. Controller 114 may then respond by generating a control signalcausing an increase or decrease in the recycle flow rate. The targetrecycle flow rate may be a dependent on an operating parameter of thetreatment system. For example, the target recycle flow rate may be amultiple of, e.g., at least two times, the influent flow rate of theincoming water to be treated.

The system and controller of one or more embodiments of the inventionprovide a versatile unit having multiple modes of operation, which canrespond to multiple inputs to increase the efficiency of the wastewatertreatment system.

The controller may be implemented using one or more computer systemswhich may be, for example, a general-purpose computer such as thosebased on in Intel PENTIUM®-type processor, a Motorola PowerPC®processor, a Hewlett-Packard PA-RISC® processor, a Sun UltraSPARC®processor, or any other type of processor or combination thereof.Alternatively, the computer system may include specially-programmed,special-purpose hardware, for example, an application-specificintegrated circuit (ASIC) or controllers intended for water treatmentsystems.

The computer system can include one or more processors typicallyconnected to one or more memory devices, which can comprise, forexample, any one or more of a disk drive memory, a flash memory device,a RAM memory device, or other device for storing data. The memory istypically used for storing programs and data during operation of thesystem 10. For example, the memory may be used for storing historicaldata relating to the parameters over a period of time, as well asoperating data. Software, including programming code that implementsembodiments of the invention, can be stored on a computer readableand/or writeable nonvolatile recording medium, and then typically copiedinto memory wherein it can then be executed by one or more processors.Such programming code may be written in any of a plurality ofprogramming languages, for example, Java, Visual Basic, C, C#, or C++,Fortran, Pascal, Eiffel, Basic, COBAL, or any of a variety ofcombinations thereof.

Components of the computer system may be coupled by one or moreinterconnection mechanisms, which may include one or more busses, e.g.,between components that are integrated within a same device, and/or anetwork, e.g., between components that reside on separate discretedevices. The interconnection mechanism typically enables communications,e.g., data, instructions, to be exchanged between components of thesystem.

The computer system can also include one or more input devices, forexample, a keyboard, mouse, trackball, microphone, touch screen, andother man-machine interface devices as well as one or more outputdevices, for example, a printing device, display screen, or speaker. Inaddition, the computer system may contain one or more interfaces thatcan connect the computer system to a communication network, in additionor as an alternative to the network that may be formed by one or more ofthe components of the system.

According to one or more embodiments of the invention, the one or moreinput devices may include sensors for measuring any one or moreparameters of system 10 and/or components thereof. Alternatively, thesensors, the metering valves and/or pumps, or all of these componentsmay be connected to a communication network that is operatively coupledto the computer system. Any one or more of the above may be coupled toanother computer system or component to communicate with the computersystem over one or more communication networks. Such a configurationpermits any sensor or signal-generating device to be located at asignificant distance from the computer system and/or allow any sensor tobe located at a significant distance from any subsystem and/or thecontroller, while still providing data therebetween. Such communicationmechanisms may be affected by utilizing any suitable technique includingbut not limited to those utilizing wireless protocols.

The controller can include one or more computer storage media such asreadable and/or writeable nonvolatile recording medium in which signalscan be stored that define a program to be executed by one or moreprocessors. The medium may, for example, be a disk or flash memory. Intypical operation, the one or more processors can cause data, such ascode that implements one or more embodiments of the invention, to beread from the storage medium into a memory that allows for faster accessto the information by the one or more processors than does medium.

Although the computer system is described by way of example as one typeof computer system upon which various aspects of the invention may bepracticed, it should be appreciated that the invention is not limited tobeing implemented in software, or on the computer system as exemplarilyshown. Indeed, rather than implemented on, for example, a generalpurpose computer system, the controller, or components or subsectionsthereof, may alternatively be implemented as a dedicated system or as adedicated programmable logic controller (PLC) or in a distributedcontrol system. Further, it should be appreciated that one or morefeatures or aspects of the invention may be implemented in software,hardware or firmware, or any combination thereof. For example, one ormore segments of an algorithm executable by controller 114 can beperformed in separate computers, which in turn, can be communicationthrough one or more networks.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. For example, an existing treatment facility may bemodified to utilize or incorporate any one or more aspects of theinvention. Accordingly, the foregoing description and drawings are byway of example only. Further, the depictions in the drawings do notlimit the inventions to the particularly illustrated representations.For example, one or more horizontally oriented filter membranes may beutilized in one or more filtration unit operations of the treatmentsystem.

Use of ordinal terms such as “first,” “second,” “third,” and the like inthe specification and claims to modify an element does not by itselfconnote any priority, precedence, or order of one element over anotheror the temporal order in which acts of a method are performed, but areused merely as labels to distinguish one element having a certain namefrom another element having a same name, but for use of the ordinalterm, to distinguish the elements.

1. A wastewater treatment system comprising: a source of wastewater; atleast one sequencing batch reactor fluidly connected to the source ofwastewater; a membrane filter system fluidly connectable to thesequencing batch reactor; and a solids reduction system comprising atleast one biological reactor fluidly connectable to the sequencing batchreactor.
 2. The system of claim 1, further comprising an equalizationtank fluidly connected between the at least one sequencing batch reactorand the membrane filter system.
 3. The system of claim 2, wherein aninlet of the at least one biological reactor is fluidly connected to asludge outlet of the at least one sequencing batch reactor.
 4. Thesystem of claim 3, wherein the solids reduction system comprises atleast one facultative biological reactor fluidly connectable to an inletof the at least one sequencing batch reactor.
 5. The system of claim 4,further comprising a solids separation system fluidly connecteddownstream of at least one of the solids reduction system and themembrane filter system.
 6. A wastewater treatment system comprising: afirst biological conversion system comprising a sequencing batch reactorfluidly connected to a membrane filtration unit; and a second biologicalconversion system fluidly connected to the first biological conversionsystem, the second biological conversion system comprising a facultativebiological reactor.
 7. The wastewater treatment system of claim 6,wherein the sequencing batch reactor is fluidly connected to a source ofa wastewater stream.
 8. The wastewater treatment system of claim 7,further comprising a solids separation unit fluidly connected downstreamof the first biological conversion system and upstream of thefacultative biological reactor.
 9. A method of treating wastewatercomprising: introducing wastewater to be treated into a biologicalreactor; aerating at least a portion of the wastewater to promoteconversion of at least a portion of undesirable components in thewastewater into a first biomass in the biological reactor; allowing atleast a portion of the first biomass to settle in the biological reactorthereby producing a solids-rich liquor and a solids-lean liquor;transferring at least a portion of the solids-lean liquor into amembrane filtration system; and transferring at least a portion of thesolids-rich liquor into a biological solids reduction system.
 10. Themethod of claim 9, further comprising retaining at least a portion ofthe solids-lean liquor in an equalization tank prior to transferringinto the membrane filtration system.
 11. The method of claim 10, furthercomprising introducing a portion of retained solids-lean liquor from themembrane filtration system into the biological reactor.
 12. The methodof claim 11, further comprising withdrawing treated water through themembrane filtration system.
 13. A method of facilitating wastewatertreatment comprising: providing a membrane filtration system comprisinga retentate liquor outlet; fluidly connecting the membrane filtrationsystem downstream of a sequencing batch reactor system; fluidlyconnecting a retentate liquor outlet of the membrane filtration systemto an inlet of the sequencing batch reactor system; and connecting asolids-reducing biological system to a sludge outlet of the sequencingbatch reactor system.
 14. The method of claim 13, wherein fluidlyconnecting the membrane filtration system comprises fluidly connectingthe sequencing batch reactor system upstream of an equalization tank andfluidly connecting the membrane filtration system downstream of theequalization tank.
 15. The method of claim 13, further comprisingconnecting a retentate outlet from the solids-reducing bioreactor systemto an inlet of the sequencing batch reactor system.
 16. The method ofclaim 15, further comprising fluidly connecting a solids separator unitdownstream of at least one of the solids-reducing biological system andthe membrane filtration system.
 17. A method of treating watercomprising: filling a basin of a sequencing batch reactor with water tobe treated to form mixed liquor; aerating the mixed liquor in the basinto promote biological activity therein; decanting from the basin asolids-lean water stream formed after allowing at least a portion of thesolids to settle into a solids-rich sludge layer; transferring at leasta portion of the solids-rich sludge into a bioreactor; and converting amicroorganism population distribution of the solids-rich sludge into afacultative-organism dominant population distribution.
 18. The method ofclaim 17, further comprising: decanting from the basin at least aportion of the solids-lean water; and contacting at least a portion ofthe decanted solids-lean water to a membrane filtration system.
 19. Themethod of claim 18, further comprising withdrawing permeate water fromthe membrane filtration system.
 20. A method of treating watercomprising: filling a basin of a sequencing batch reactor with water tobe treated to form mixed liquor; aerating the mixed liquor in the basinto promote biological activity therein; allowing at least a portion ofthe solids in the mixed liquor to settle into a solids-rich sludge layerbelow a solids-lean water layer; decanting at least a portion of thesolids-lean water; and contacting the decanted solids-lean water to amembrane filtration system.
 21. The method of claim 20, furthercomprising promoting growth of facultative microorganisms over obligateaerobic microorganism in at least a portion of the solids-rich sludge.